Broadband slotted waveguide antenna array

ABSTRACT

A means for broadening the bandwidth of a waveguide slot array by introducing a pair of metallic phase shifter probes between adjacent radiating slots located in the feeding waveguide. The probes are made to penetrate to specific depths within the waveguide thereby effectively restoring the electrical phase between the slots and tuning the array whenever the operating frequency substantially deviates from a predetermined frequency which determines the slot spacing.

United States Patent 1 McComas et a1.

[ 51 Feb. 13, 1973 BROADBAND SLOTTED WAVEGUIDE ANTENNA ARRAY inventors: Hall R. McComas, Laurel; John H.

Staehlin, Baltimore, both of Md.

Westinghouse Electric Corporation, Pittsburgh, Pa.

Filed: Oct. 20, 1970 Appl. No.: 82,446.

Assignee:

References Cited UNITED STATES PATENTS Primary Examiner-Eli Lieberman Attorney-F. l-l. Henson, E. P. Klipfel and J. L. Wiegreffe [57] ABSTRACT A means for broadening the bandwidth of a waveguide slot array by introducing a pair of metallic phase shifter probes between adjacent radiating slots located in the feeding waveguide. The probes are made to penetrate to specific depths within the waveguide thereby effectively restoring the electrical phase between the slots and tuning the array whenever the operating frequency substantially deviates from a predetermined frequency which determines the slot spacing.

10 Claims, 3 Drawing Figures PATENTED FEB 1 3191s- SHEET 2 or 2 I. H R iir 1; v r -IMEW r @w wwqm mw BROADBAND SLOTTED WAVEGUIDE ANTENNA ARRAY BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to microwave apparatus of the type generally employing radiating electromagnetic energy and more particularly to a slotted waveguide antenna array wherein electromagnetic energy is radiated from a plurality of inclined slots located in a common sidewall of a feeding waveguide and which additionally includes means for broadbanding the array so as to permit optimum operation for frequency shifts away from a predetermined operating frequency.

2. Summary Briefly, the subject invention comprises at least one waveguide member adapted to be fed electromagnetic radiation at microwave frequencies. The waveguide member includes a plurality of angulated radiating slots commonly located in one sidewall and respectively spaced from one another by substantially one half wavelength of a predetermined operating frequency. A moveable pair of metallic phase shifter probes are mounted on an adjacent sidewall between adjacent slots along the center line of the adjacent sidewall. Each probe is located substantially one quarter of a slot spacing away from its nearest slot. The phase shifter probes are coupled to actuator means for being selectively inserted into and retracted from the interior of the waveguide member for effectively changing the electrical phase between the slots for a frequency deviation from said predetermined frequency. The actuator means comprises a linkeage arm including a cam follower which engages a multi-step cam surface located in a flat cam rod which extends along the length of the waveguide member externally thereto and which is adapted to be driven in a selected longitudinal direction with respect to the waveguide member and thereby move the probes into and out of the waveguide member accordingly.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary front elevation, partly in section, showing a microwave antenna array;

FIG. 2 is a transverse vertical section of the array shown in FIG. 1 taken along the lines 2-2 thereof; and

FIG. 3 is a fragmentary vertical section of the array shown in FIG. 1 taken along the line 3-3 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings and more particularly to FIGS. 1 and 2, there is shown a portion of a microwave antenna array comprising a plurality of slotted waveguides arranged in mutual parallel relationship. The figures disclose three microwave waveguide members 10, 12 and 14 separated by support channels 16 and 18 such as shown in detail in FIG. 2. Although three waveguide members are disclosed, any suitable number may be utilized when desirable. One sidewall 20, 22 and 24 of the waveguide members 10, 12 and 14, respectively, overlap forming a wall 21 and 23 respectively of the channels 16 and 18. The opposite sidewalls 26, 28 and 30 of the waveguide members 10, I2 and 14 each include a plurality of angularly inclined radiating slots 32 such as shown in FIGS. 1 and 3 which are mutually spaced substantially V4 wavelength (M2) of the desired operating frequency, that is the frequency of the electromagnetic microwave energy which is fed into the waveguide members 10, 12 and 14 from a microwave source not shown. Slotted waveguide antennas of this type are well known to those skilled in the art; therefore, little else needs to be said about such apparatus, except that as the operating frequency deviates from the predetermined value which in turn determines the slot spacing parameter M2 or the phase interval between adjacent slots changes. Therefore a limitation in operational bandwidth results from these phase perturbations accumulating to a large value over the total length of each waveguide member of the array.

It is the object of the present invention, accordingly, to provide a means for changing the electrical spacing between the slots 32 for restoring each phase shift to the required 180 or M2 for changes in operational frequency within a selected range. This is accomplished by means of adjustably varying the penetration of a pair of metallic phase shifter probes 34 and 36 in the form of solid cylindrical rods located between adjacent slots 32 along the center line of the lower broadwall 38 and 40, respectively of the waveguide members 10 and 12. The probes 34 and 36 are made to penetrate to specific depths providing correction at discrete frequency shifts. This is accomplished for the waveguide members 10 and 12 by means of elongated flat metallic bar cam members 41 and 42 which include a plurality of three step cam surfaces 44 machined into the broad faces 45 and 46 along their length. The cam members 41 and 42 are adapted to run beneath the respective waveguide members 10 and 12 substantially parallel to the lower broadwalls 38 and 40. This is provided by means of mounting the cam members 41 and 42 on respective metal face plates 47 and 48 of the channels 16 and 18 which include upper and lower ball bearings 50 located in rearwardly facing projections on the plates 47 and 48. This is illustrated for example in FIG. 2.

In the preferred embodiment of the subject invention, two pairs of phase shifter probes 34 and 36 are coupled to a common pin support linkeage arm 52 by engaging a rectangular slot 54 shown in FIG. 2 at the lower extremities of the probes 34 and '36 with connection being made by means of the pins 56. The support linkeage arm 52 additionally includes two cam followers 58, each located midway between a respective pair of probes 34 and 36. The cam followers 58 are adapted to engage a respective cam surface 44 such as shown in FIG. 3 so that longitudinal movement of the cam members 41 and 42 will effect an upward or downward movement of the probes 34 and 36 through the metal collars 60 and bushings 62 as shown in FIGS. 1 and 2. V

The flat cam members 41 and 42 extend substantially the full length of each radiating element comprising the waveguide members 10 and I2 and actuation thereof causes all of the probe sets 34 and 36 respectively coupled thereto to move simultaneously causing the entire array face to be tuned to a new frequency depending upon the amount of penetration of the probe sets into the respective waveguide member.

The cam surfaces 44 shown in FIGS. 1 and 3 include three steady state positions or regions 64, 66 and 68 with two transition regions 70 and 72 therebetween. The fixed regions 64 and 68 appear at the extremities of the cam surface 44 with the fixed region 66 appearing intermediate thereof. FIG. 3 illustrates both extreme positions. For example, the probe sets 34 and 36 associated with the waveguide member 10 are shown fully extended and penetrating into the interior of the waveguide member 10. This occurs when the cam follower member 58 is engaging the region 64 of the cam surface 44. The probe set 34 and 36 associated with the lower waveguide member 12, on the other hand, as shown in FlG.. 3 are fully retracted with the cam follower 58 engaging the region 68. This is done for purposes of illustration since normal operation would have the cam members 41 and 42 actuated in an identical manner.

By suitably actuating the cam members 41 and 42 for example by means of digital type hydraulic pistons, not shown, positive motion of the rods can be obtained so that the cam followers 58 are adapted'to effect three steady state tuning positions for the probes 34 and 36, that is, when they are retracted, partially inserted, and fully inserted into the respective waveguides. While this means of compensation does not correct for the frequency sensitivity of the slots 32 themselves for which the useful bandwidth is in the order of to percent, the present invention, however, is a substantial improvement over the l to 2 percent bandwidth obtained without compensation.

What has been shown and described, therefore, is a improved means for substantially broadening the bandwidth of a microwave slotted antenna array, thereby eliminating one of the major disadvantages heretofore associated with such apparatus.

We claim as our invention:

1. A phase shifter for broadbanding a microwave slot array comprising, in combination:

at least one slotted waveguide member adapted to receive andradiate microwave energy therefrom and including a plurality of radiating slots located in one wall thereof and having a predetermined mutual spacing therebetween corresponding to a half wavelength of one operating frequency of said microwave energy;

first means comprising metallic phase shift probes disposed between each of said radiating slots and adapted to penetrate into said waveguide member through a wall adjacent to said one wall for effectively changing the electrical spacing between each of said plurality of radiating slots in accordance with a variation in the frequency of said microwave energy relative to said one operating frequency, said phase probes being spaced substantially one quarter of the distance between slots away from an adjacent slot; and

second means coupled to said first means for selectively varying the depth of penetration of each of said phase shift probes into said waveguide member.

2. The invention as defined by claim 1 wherein said phase shift probes comprises metallic probes selectively positioned between adjacent slots of said plurality of radiating slots.

3. The invention as defined by claim 2 wherein said phase shifter probes comprises a pair of metallic probes respectively spaced substantially one quarter of the distance between slots away from an adjacent radiating slot.

4. A phase shifter for broadbanding a microwave antenna slot array comprising, in combination:

at least one slotted waveguide member adapted to receive and radiate microwave energy therefrom and including a plurality of radiating slots located in one wall thereof and having a predetermined mutual spacing therebetween corresponding to a half wavelength of one operating frequency by said microwave energy;

first phase shifter means adapted to penetrate into said waveguide member through a wall adjacent to said one wall for effectively changing the electrical spacing between said plurality of radiating slots, said phase shifter means comprising a pair of metallic cylindrical rods with each of said rods being respectively spaced substantially one 'quarter of the distance between slots away from an adjacent radiating slot; and

second means coupled to said phase shift means for selectively varying the depth of penetration of each of said metallic cylindrical rods into said waveguide member.

5. The invention as defined by claim 4 and wherein said second means additionally includes a linkeage arm coupled between said pair of probes for varying the depth of penetration of said probes simultaneously.

6. The invention as defined by claim 5 and additionally including means coupled to said linkeage arm for selectively moving said pair of probes to a first and second steady state position.

7. The invention as defined by claim 6 wherein said last-mentioned means includes a cam follower coupled to said linkeage, and cam means in contact with said cam follower for driving said pair of probes to said first and second position.

8. The invention as defined by claim 7 wherein said cam means includes at least a first and a second cam surface region for effecting a fully retracted and a fully inserted steady state position of said pair of probes.

9. The invention as defined by claim 8 wherein said cam means comprises an elongated member having said first and second cam surface regions machined in one face thereof, said elongated member vbeing mounted beneath said wall adjacent to said one wall of said waveguide member and adapted to be moved longitudinally with respect thereto, said longitudinal movement providing movement of said probes in and out of said waveguide member.

10. The invention as defined by claim 9 wherein said elongated member additionally includes a third cam surface located intermediate said at least two cam surfaces for providing a partly inserted steady state position of said pair of probes into said waveguide member.

l t i i l 

1. A phase shifter for broadbanding a microwave slot array comprising, in combination: at least one slotted waveguide member adapted to receive and radiate microwave energy therefrom and including a plurality of radiating slots located in one wall thereof and having a predetermined mutual spacing therebetween corresponding to a half wavelength of one operating frequency of said microwave energy; first means comprising metallic phase shift probes disposed between each of said radiating slots and adapted to penetrate into said waveguide member through a wall adjacent to said one wall for effectively changing the electrical spacing between each of said plurality of radiating slots in accordance with a variation in the frequency of said microwave energy relative to said one operating frequency, said phase probes being spaced substantially one quarter of the distance between slots away from an adjacent slot; and second means coupled to said first means for selectively varying the depth of penetration of each of said phase shift probes into said waveguide member.
 1. A phase shifter for broadbanding a microwave slot array comprising, in combination: at least one slotted waveguide member adapted to receive and radiate microwave energy therefrom and including a plurality of radiating slots located in one wall thereof and having a predetermined mutual spacing therebetween corresponding to a half wavelength of one operating frequency of said microwave energy; first means comprising metallic phase shift probes disposed between each of said radiating slots and adapted to penetrate into said waveguide member through a wall adjacent to said one wall for effectively changing the electrical spacing between each of said plurality of radiating slots in accordance with a variation in the frequency of said microwave energy relative to said one operating frequency, said phase probes being spaced substantially one quarter of the distance between slots away from an adjacent slot; and second means coupled to said first means for selectively varying the depth of penetration of each of said phase shift probes into said waveguide member.
 2. The invention as defined by claim 1 wherein said phase shift probes comprises metallic probes selectively positioned between adjacent slots of said plurality of radiating slots.
 3. The invention as defined by claim 2 wherein said phase shifter probes comprises a pair of metallic probes respectively spaced substantially one quarter of the distance between slots away from an adjacent radiating slot.
 4. A phase shifter for broadbanding a microwave antenna slot array comprising, in combination: at least one slotted waveguide member adapted to receive and radiate microwave energy therefrom and including a plurality of radiating slots located in one wall thereof and having a predetermined mutual spacing therebetween corresponding to a half wavelength of one operating frequency by said microwave energy; first phase shifter means adapted to penetrate into said waveguide member through a wall adjacent to said one wall for effectively changing the electrical spacing between said plurality of radiating slots, said phase shifter means comprising a pair of metallic cylindrical rods with each of said rods being respectively spaced substantially one quarter of the distance between slots away from an adjacent radiating slot; and second means coupled to said phase shift means for selectively varying the depth of penetration of each of said metallic cylindrical rods into said waveguide member.
 5. The invention as defined by claim 4 and wherein said second means additionally includEs a linkeage arm coupled between said pair of probes for varying the depth of penetration of said probes simultaneously.
 6. The invention as defined by claim 5 and additionally including means coupled to said linkeage arm for selectively moving said pair of probes to a first and second steady state position.
 7. The invention as defined by claim 6 wherein said last-mentioned means includes a cam follower coupled to said linkeage, and cam means in contact with said cam follower for driving said pair of probes to said first and second position.
 8. The invention as defined by claim 7 wherein said cam means includes at least a first and a second cam surface region for effecting a fully retracted and a fully inserted steady state position of said pair of probes.
 9. The invention as defined by claim 8 wherein said cam means comprises an elongated member having said first and second cam surface regions machined in one face thereof, said elongated member being mounted beneath said wall adjacent to said one wall of said waveguide member and adapted to be moved longitudinally with respect thereto, said longitudinal movement providing movement of said probes in and out of said waveguide member. 